This invention relates to a method of making an implanted resistor, as well as to a resistor obtained with that method.
As is known, to make resistive elements in a semiconductor substrate or chip, in particular high Ohmic value resistors, for use as integrated resistive circuit components to be circuitally connected, for example, to such active components as transistors, several techniques are currently employed the most common of which are the making of such resistors following diffusion of the emitter resions, that is on completion of the process and their making prior to deposition and diffusion of the base and emitter regions.
In the former prior method, the resistor is generally obtained by phototreatment on the field oxide, which has a significant thickness. This fact may give rise to the problem of interruptions of any metal layers or connections (hereafter called "metals") crossing the resistor; in addition, if the metal crossing the resistor is at a high potential, undesired variations in the Ohmic value of the resistor may also occur.
Vice versa, with the latter prior method mentioned above, the resistors are made, as mentioned, after the deposition and diffusion of the base and emitter regions. In this case, the substantial drawback is encountered that the Ohmic value of the resistance depends on such thermal treatments as successive oxidations.